The Walking Dead creator Robert Kirkman told Comic Book Resources this week that digital sales are now 25% to 30% of his comic and graphic novel sales.  "[W]hen it started at comiXology, we were doing 5% and as we’ve continued to work with comiXology and branched out into other digital platforms, we’ve seen digital sales go from 5% of print sales to we’re getting close to 25 to 30% of print sales," he said. Kirkman said he was also seeing the trend on his other titles, such as Invincible.
Of course, the print versions are also bestsellers, both in the bookstore market (see "Nothing Can Stop 'The Walking Dead'") and the comic store market (see "Top 300 Graphic Novels--November 2012").

Digital sales of 25% to 30% of total sales are higher than other publishers have been reporting (see, for example, "Interview with IDW’s Ted Adams," in which Adams revealed earlier this year that digital was 10% of IDW’s sales).  But media-driven properties have been among the bestselling digital comics, perhaps because digital comics are easier to find for consumers that don’t regularly visit comic or book stores.
Kirkman said that the show was also driving new consumers into comic stores.  "I’m hearing from lot of comic book shops that there are new people that they haven’t seen before coming in and seeking out The Walking Dead comics," he said.
The show is currently in a break between the first and second halves of its third season, and is the #1 show, cable or broadcast, for adults 18 to 49 (see "'TWD' the Top Fall Series").
--Disclosure: ICv2 has a business relationship with comiXology as a representative for its Retailer Tools; ICv2 CEO Milton Griepp also serves on the board of comiXology.